In January, 2004, a 71-year-old Chinese man was admitted to hospital because of fever and chills for two days associated with sore throat, rhinorrhoea, productive cough with purulent sputum, headache and nausea. He had history of pulmonary tuberculosis more than 40 years ago complicated by cicatrization of right upper lobe and bronchiectasis with chronic Pseudomonas aeruginosa colonization of airways. He was a chronic smoker and also had chronic obstructive airway disease, hyperlipidemia, and asymptomatic abdominal aortic aneurysm. He had just returned from Shenzhen of China three days before admission. During his three-day trip to Shenzhen, he had no history of contact with or consumption of wild animals. On admission, his oral temperature was 37.6° C. Physical examination showed tracheal deviation to the right and inspiratory crackles over the anterior left lower zone. His haemoglobin level was 14.7 g/dL, total white cell count 12.1×109/L, with neutrophil 9.7×109/L, lymphocyte 1.6×109/L and monocyte 0.5×109/L, and plate count 303×109/L. His liver and renal function tests were within normal limits. Chest radiograph showed right upper lobe collapse and new patchy infiltrates over the left lower zone. Blood culture was performed. Empirical oral amoxicillin/clavulanate and azithromycin were commenced. Nasopharyngeal aspirates for direct antigen detection for respiratory viruses, RT-PCR for influenza A virus, human metapneumovirus and SARS-CoV, and viral cultures were negative. Sputum for bacterial culture only recovered P. aeruginosa. Sputum for mycobacterial culture was negative. Blood culture was negative. Paired sera for antibodies against Mycoplasma, Chlamydia, Legionella, and SARS-CoV did not show any rise in antibody titres. His fever subsided two days after admission. His cough improved and he was discharged after five days of hospitalization. Amoxicillin/clavulanate and azithromycin were continued for a total of seven days. The present inventors were the group involved in the investigation of this patient. All tests for identifying commonly recognized viruses and bacteria were negative in these patients. The etiologic agent responsible for this disease was not known until the complete genome of CoV-HKU1 from this patient by the present inventors as disclosed herein. Namely, the present invention discloses a novel human virus that has been identified from a patient suffering from pneumonia. The invention is useful in both clinical and scientific research applications.